1. Field of the Invention
The invention is directed to an improved method for protecting an electric motor and/or its trigger circuit against overload, and on a circuit arrangement for performing such a method.
2. Description of the Prior Art
German Patent Disclosure DE 199 44 194 A discloses an overload protector for an electronically commutable motor whose end stage can be triggered via an electronic control unit by means of PWM control signals and can be supplied with a supply voltage. A limitation to a maximal load with overload protection of the motor is attained by providing that as a function of the magnitude of the supply voltage and of the specified set-point value, for the PWM control signals at least from the time the rated voltage of the motor is exceeded, the pulse width of the pulse width modulated (PWM) control signals for the end stage is reduced to values that prevent an overload of the motor and of the electronic components by limiting the motor power. However, a circuit arrangement of this kind assures overload protection only as long as the triggering of the end stage by PWM signals does not itself have any malfunctions.